One of the most common builder errors that home inspectors have to deal with is the installation of concrete surfaces over the top of wood siding—or any kind of siding for that matter.
It is not a good idea.
That bears repeating: IT IS NOT A GOOD IDEA.
Since so many builders install concrete in this manner, there is a perception, in the real estate community, that it must be OK. It is assumed that, at best, home inspectors are tilting at windmills for even bringing it up.
When I see concrete poured over siding, the information goes in the report. I know that 99% of the time nothing is going to be done about it. In well protected areas it might not even represent that big of a deal and of course some climates are more forgiving than others. I must offer a caution however, that given the right amount of wind driven rain, sprinkler systems or wet soils under the concrete work, problems can arise over time.
All parties want to hide their heads in the sand over the issue because of how difficult it is to make satisfactory repairs.
Take a look at the following picture.
Can you see that this concrete stoop covers three rows of siding and that the fourth row sits right on top of the concrete? While it may not be obvious to anyone that has not framed houses, you should be able to tell by where the door sill is that the stoop also covers the rim joist of the floor system. This means that we have not only the siding behind the concrete but the house sheathing and floor system are also behind the concrete.
What you are looking at is a totally typical installation that I see on just about every other inspection.
So what is the solution?
Well of course the best solution is to remove all the concrete and start over. All the wood materials that are going to be behind the concrete should be pressure treated lumber and properly flashed behind the concrete with metal flashings that will last “forever.” These metal flashings should be over a foundation grade rubber membrane. There should be proper clearances to wood siding all around the concrete work leaving the metal flashing visible. This would be considered “best practice.” We should think of these house components as being below grade—because in a very real sense they are.
So, since we know that this repair is not going to happen, what is the next best thing to “try” to do? I say “try” because anything short of “best practice” is never going to get warranted by a builder that knows what they are doing—at least one that is planning on being in the business for a long time.
One approach that I see sometimes is to caulk the connection with the wood and the concrete. We all know about the longevity of caulk—so this is not the best long term solution. Another thing that caulking does, besides preventing water from flooding behind the concrete work, is that it prevents moisture from the ground from having a way out from behind the concrete, thus promoting elevated moisture in the wood behind the concrete. Caulking the connection may not accomplish the desired result and may actually make matters worse.
Another approach that I like better is to remove as much of the siding as possible and insert appropriate flashings that extend out over the concrete work. A vapor permeable weather-stripping could be installed between the concrete and the flashing. This will keep most surface water out and prevent moisture from being trapped behind the concrete—somewhat.
Of course doorways that are flush with the concrete are not likely going to get addressed in this scenario and no one is likely going to remove the doors to properly flash them as is necessary.
Again, as we have discussed, this solution is not ideal, but in light of no one being willing to make proper repairs it may be the “solution” we are stuck with.
Just in case you are wondering just how much damage can “really” happen, or whether I am truly merely tilting at windmills, here are a couple of pictures of the actual damage that has been partially uncovered in the area behind the stoop pictured above.
There was evidence of Moisture Ants, Carpenter Ants, Dampwood Termites and Wood Decay/Rot all involved in this damage. At the exterior of the home—right where one of the siding boards disappears behind the concrete stoop there is a Carpenter Ant “window” visible if you know where to look. They make these windows for kicking out frass and for coming and going. Sometimes I think they might actually BE windows—but I am not an ant.
The white color in the next picture is the concrete stoop itself that is visible where the rim joist and sheathing have been completely destroyed.
So while I may be tilting at windmills the wind is blowing in my favor.
By Charles Buell, Real Estate Inspections in Seattle
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